In automation technology, electronic terminal blocks which will in the following also be referred to as bus terminals are used to connect sensors and actuators which provide or, respectively, request various signals via analogue and digital inputs and outputs to a control unit via a field bus without further wiring. The electronic terminal blocks serve to bundle the various sensor signals and to forward them to the control unit by means of a standardized bus signal or, respectively, to transduce the control commands of the control unit into corresponding signals for the actuators and to forward the signals to the actuators.
In this context, the electronic terminal blocks are frequently integrated on a shared carrier rail as a bus-terminal station wherein a bus coupler is provided as a head end, the bus coupler serving as an interface to the field bus and connecting the electronic terminal blocks to the control unit. The communication between the bus couplers and the individual electronic terminal blocks is carried out via an internal terminal bus wherein the bus-terminal connection is carried out via contacts in a wireless manner.
Bus-terminal stations normally allow for serially connecting electronic terminal blocks having a whole range of signal types. Another possibility is to back-fit the bus-terminal station with further bus terminals. Individual electronic terminal blocks may furthermore have their own intelligence in order to be able to carry out control tasks in a de-centralized manner without any interference from the control unit. Moreover, the bus-terminal station may comprise specific terminal blocks which are capable of directly addressing the power units of an automated system.
DE4402002A1 discloses a bus-terminal station in which electronic terminal blocks may be locked onto a carrier rail. In this arrangement, the individual terminal blocks comprise internal data-bus and current-supply lines which are dragged through the terminal housing, while contacts for the data-bus line and the current line are respectively provided at the side faces of the housing. By sliding the terminal blocks next to one another on the carrier rail, the contacts between the terminal blocks are automatically connected, thus forming continuous data-bus and supply lines.
Electronic terminal blocks are normally produced with a plastic housing. Due to electromagnetic shielding and heat development occurring in process technology, however, it is in many cases not possible to use such plastic electronic terminal blocks for measuring.
A bus-terminal station by the name of imc CRONOSflex is known in which the electrical terminal blocks have a metal housing which allows for use in a difficult process environment. The self-supporting metal housing of the electronic terminal blocks hereby has laterally elongated front and back plates forming a click mechanism in order to connect the electronic terminal blocks within the framework of the bus-terminal station. The data-bus and current-line contacts are arranged in the laterally protruding back plates and are plugged to the corresponding contacts of adjacent terminal blocks during assembly. However, in the imc CRONOSflex system gaps occur between the assembled electronic terminal blocks, thus increasing the installation size of the bus-terminal station. The click mechanism used during assembly additionally requires that when the bus-terminal station is enlarged, the further electronic terminal blocks be continuously added laterally to the already existing electronic terminal blocks, resulting in the fact that the arrangement of the electronic terminal blocks cannot be changed in a flexible manner.